1. Field of the Invention
The present invention relates to a plasma lighting system having a thin metallic film resonator, and more particularly, to a plasma lighting system having a thin metallic film resonator, which can raise the luminous efficiency of an electrodeless bulb by increasing the amount of microwaves to be focused on the electrodeless bulb, and which can avoid malfunctions of other external devices in the same frequency band by preventing microwaves from leaking out of the resonator.
2. Description of the Background Art
Generally, a plasma lighting system is a lighting system in which microwave energy generated from a magnetron, a microwave generator, is transmitted to a resonator through a waveguide, and is applied to an electrodeless bulb installed in the resonator so that gas filled in the electrodeless bulb is excited and converted into a plasma state to generate light.
The electrodeless bulb does not include an electrode or a filament therein, thus the plasma lighting system has longer or semipermanent life span. The filler material filled in the electrodeless bulb emit light by being transformed into a plasma state to thus generate light that closely resembles natural light.
FIG. 1 is a plane view showing a structure of a conventional plasma lighting system. FIG. 2 is a line cross-sectional view taken along line 11-11 of FIG. 1.
As shown therein, the conventional plasma lighting system includes: a high voltage generator 20 generating a high voltage when electric power is applied to an inner space of a casing 10; a microwave generator 30 generating a microwave having a high frequency when the high voltage generated from the high voltage generator 20 is applied; a waveguide 40 guiding the microwave applied from the microwave generator 30; a resonator 50 provided outside the casing, for shielding the microwave guided by the waveguide 40 from being leaked out to provide a resonance mode; and an electrodeless bulb 60 rotatably arranged at the center of the resonator 50, for generating light by transforming inert gas enclosed therein into a plasma state.
The waveguide 40 is a cylindrical tube, whose one side is connected to the microwave generator 30. A resonator coupling member 41 having a predetermined height is protruded on the upper end face of the waveguide 40 along the height direction of the waveguide 40.
The resonator coupling member 41 is formed in a ring shape having a smaller diameter than the waveguide 40, the center of which is penetrated at the center, and an outer surface of which is fixed and coupled to the resonator 50.
The resonator 50 is formed of a cylindrical mesh 51 having a net structure so that the electrodeless bulb 60 is housed in an inner space, the microwave is blocked from being leaked out and then transmitted to the electrodeless bulb 60, and the light generated from the electrodeless bulb 60 can be transmitted to the outside. The outer profile of the resonator 50 is formed of steel so as to maintain its cylindrical form.
A mirror 70 is formed in a disc shape having the same diameter as the resonator coupling member 41, and arranged so as to be in contact with the upper end face of the resonator coupling member 41. The electrodeless bulb 60 is provided at the center of the mirror 70 so as to extend to a predetermined length along the height direction of the waveguide 40 and be exposed to the outside of the waveguide 40.
Meanwhile, the electrodeless bulb 60 includes a bulb-shaped luminous unit 61 having a predetermined inner volume in which a filler material is enclosed, and a fixing unit 62 extended integral with the luminous unit 61 and formed of the same material as the luminous unit 61.
The luminous unit 61 is installed inside the casing 10, and the fixing unit 62 is installed to penetrate through the center portion of the waveguide 40. The fixing unit 62 installed together with the luminous unit 61 is connected to a motor shaft of a driving motor 90 installed in the casing 10 and rotates at a predetermined speed.
Preferably, the luminous unit 61 is mainly made of a material, such as quartz, having a high transmittance and an extremely small dielectric loss. The filler material to be enclosed in the luminous unit 61 is mainly made of luminous materials, such as metal, halogen compound, sulphur, and selenium, inert gases, such as argon gas and krypton gas, for forming plasma in the luminous unit 61, and discharge solvent materials, such as mercury, for making lighting easier by assisting an initial discharge or controlling the spectrum of generated light or the like.
In the drawings, unexplained reference numerals 70 denotes a mirror, 80 denotes a reflecting shade, 100 denotes a cooling fan, 110 denotes a second driving motor for rotating the cooling fan, and 120 denotes an air duct.
According to the above-said construction of the conventional plasma lighting system, when a driving signal is inputted to the high voltage generator 20, the high voltage generator 20 raises AC power and supplies the raised high voltage to the microwave generator 30. The microwave generator 30 oscillates by a high voltage to thereby generate microwaves having a very high frequency.
The microwaves are emitted into the resonator 50 through the waveguide 40, and then the inert gas filled in the electrodeless bulb 60 is excited to continually transform the luminous material into a plasma state so as to emit light having an intrinsic emission spectrum. The light reaches the surface of the mirror 70 arranged at the rear side of the electrodeless bulb 60 and is reflected on the front side of the electrodeless bulb 60, thereby lighting a space.
However, in such a conventional plasma lighting system, if the microwaves generated in the microwave generator 30 are guided by the waveguide 40 to provide a resonance mode inside the resonator 50, parts of the microwaves are leaked out via openings of the mesh 51 of the resonator 50 and thus, the amount of microwaves to be focused on the electrodeless bulb 60 is reduced, thereby decreasing the optical efficiency of the electrodeless bulb 60. Further, malfunctions may occurred to other external devices in the same frequency band with the leaked microwaves.